Broken links in changelogs

[alamb]

Describe the bug

The changelogs have links such as the following https://datafusion.apache.org/library-user-guide/upgrading.html

However, that page no longer exists

The new URL is: It looks like the pages are now:
https://datafusion.apache.org/library-user-guide/upgrading/index.html

To Reproduce

For example: https://github.com/apache/datafusion/blob/main/dev/changelog/51.0.0.md

Says

See the upgrade guide for information on how to upgrade from previous versions.

However, that link is https://datafusion.apache.org/library-user-guide/upgrading.html which is broken

Expected behavior

The link should go to a real page

It looks like the pages are now:
https://datafusion.apache.org/library-user-guide/upgrading/index.html

Ideally we would be able to make the old URLs work (perhaps with a http redirect) rather than just changing the old changelog files

Additional context

This was probably introduced by

• Break upgrade guides into separate pages #20183